[llvm] r201559 - GlobalMerge: move "-global-merge" option to the pass itself.

[Tim Northover]

> Having looked at this recently, is there any particular reason why
> GlobalMerging has its own "disable me" flag anyway? Wouldn't it be best to
> just remove this flag completely?

Well, it can make assembly output less readable I suppose, but really
I'd prefer to move the other way if anything. llc is rather monolithic
in what it does.

Cheers.

Tim.